1. Field of the Invention
This invention relates generally to power plants which derive power from the immense pressure of water in the ocean's depths and, more particularly, to submersible power plants having a pump activated by ocean swells to evacuate water from the submersed power plant.
2. Description of the Related Art
The development of renewable energy resources has taken on increased importance as the supply of fossil fuels grows ever closer to being exhausted. Given the increasing evidence of the harmful effects on the environment attendant to consumption of conventional fuels, it is imperative that newly developed sources of energy be clean and reliable.
A great deal of salutary and creative effort has been directed to harnessing the powers of nature. These efforts, such as solar power, hold promise but today still leave us largely dependent on foreign oil. One force of nature that remains untapped is the energy trapped in the earth's oceans where deep sea water is subject to immense pressures. It is generally understood that an enclosure may be submerged in the sea and that water flowing into the enclosure at high pressure may be used to power a turbine for generation of electricity. The problem of how to remove the water from the enclosure has been addressed with attempted solutions having varying levels of complexity and practicality.
In U.S. Pat. No. 3,994,134 to Molnar, an apparatus for power generation in deep seawater is disclosed in a first cycle of which water filling a submerged receptacle chamber passes through a rotating power generator. In a second cycle an electric motor moves receptacle and plunger casings simultaneously downward on angularly positioned border plates with the result that a plunger is pushed into the receptacle chamber to force out water from the chamber. In a third cycle the receptacle and plunger casings are simultaneously moved upwards on the border plates, assisted by a counterweight suspended on a cable, to pull the plunger out of the chamber. Compressed gas is pumped into the chamber during the upward movement to avoid creating a vacuum in the chamber. The complexity of the Molnar apparatus would make it impracticable to employ in a deep sea environment. Another disadvantage is that the Molnar apparatus pumps intermittently, as the receptacle moves through the downward and upward cycles, greatly reducing its efficiency. Finally, supplemental sources of energy such as compressed gas and electric motors to assist the component parts of the device in moving through its cycles are needed which diminishes the overall energy efficiency of the device.
U.S. Pat. No. 4,091,618 to Jackson discloses an ocean motion power generating system in which a container is positioned beneath the surface of a body of water. A hydrostatic head caused by the pressure differential between water surrounding the container and a void inside the container causes water to flow into the container through an inlet pipe and then through a turbine which drives a generator. The void is created by pumping water out of the container. The pump involves a floating buoy, the action of wave motion on which causes the buoy to rise and fall. A piston is joined to the buoy by a depending cable so that, when the buoy moves upward, the piston is pulled upward in a cylinder. As the piston is pulled up a number of check valves in the form of individual vanes open to allow water from the container to flow into the cylinder. As the piston falls downward, apparently due to the force of gravity, the vanes close to prevent water from flowing back into the container, and like check valves in the piston head open to allow water in the cylinder to pass into the ocean. The vanes in the piston head close when the piston is pulled up, preventing water from the ocean to enter the cylinder. In an alternate embodiment of Jackson, the buoy is deployed in the shape of a cylindrical collar around a leg of an ocean platform. The Jackson apparatus has a number of disadvantages. First, it is unclear how a void could ever be created given the device as disclosed because, as the piston draws water out of the container, replacement water is drawn in through the inlet pipe. Regardless of whether a true void is created in Jackson., the pressure in the container will fluctuate continuously according to the siphoning power acting on the container as a result of the upward movement of the piston leading to uneven pumping action. Second, the amount of power necessary to efficiently evacuate water from the container becomes increasingly tremendous as the container is submerged further in the ocean. The power stroke of the piston in Jackson is on upward movement so that the piston is pulling, not only against the pressure of the ocean versus the lower pressure of the interior of the container, but against the force of gravity. Were container to descend further in the ocean, a depth would be reached at which point it would become impossible for the piston, driven by the rising buoy, to remove water from the container. Third, in an ocean setting, especially at substantial depths, mechanical wear and tear and part failure is a very serious concern. The multiple vanes which comprise the check valves in the piston and between the container and the cylinder in Jackson would appear to be prone to failure in such a deep sea environment. Fourth, use of a cable to suspend the piston from the buoy permits substantial lateral movement and, even in the ocean platform-based embodiment, introduces the potential for flexure of the cable leading to the possibility of the cable becoming tangled, dropping or the cable failing under high recovery stresses. Fifth, cables are subject to deterioration over time and require maintenance or replacement. Finally, the pump in Jackson acts intermittently such that the hydrostatic head will increase or decrease according to the upward and downward movements of the piston, with resulting decreased efficiency.
U.S. Pat. No. 4,619,593, also to Molnar, discloses a tank which is submerged in deep sea water such that the pressure within the tank is less than that of the pressure of water in the surrounding sea. Water flowing from the sea into the tank actuates a turbine for producing work. A fluid extraction device uses a reciprocating extractor pocket to move water from within the tank to the sea outside. The fluid extractor requires a motor to move it back and forth and uses three sets of valves to admit water from the tank into the extractor pocket, move the extractor pocket outside of the tank, and release the water into the sea.
The state of the art leaves an unmet need for an deep sea power generating apparatus that is efficient, relies to the smallest extent possible on external power sources, is simple, produces continuous, rather than intermittent, power, and is durable in an ocean deep water setting.